| Message ID | 20220718025826.29148-1-lizhijian@fujitsu.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | ksefltest: pidfd: Fix wait_states: Test terminated by timeout | expand |
On 18/07/2022 10:58, Li, Zhijian/ζ ζΊε wrote: > 0Day/LKP observed that the kselftest blocks forever since one of the > pidfd_wait doesn't terminate in 1 of 30 runs. After digging into > the source, we found that it blocks at: > ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WCONTINUED, NULL), 0); > > wait_states has below testing flow: > CHILD PARENT > ---------------+-------------- > 1 STOP itself > 2 WAIT for CHILD STOPPED > 3 SIGNAL CHILD to CONT > 4 CONT > 5 STOP itself > 5' WAIT for CHILD CONT > 6 WAIT for CHILD STOPPED > > The problem is that the kernel cannot ensure the order of 5 and 5', once > 5's goes first, the test will fail. Correct: s/once 5's goes first/once 5 goes first > > we can reproduce it by: > $ while true; do make run_tests -C pidfd; done > > Introduce a blocking read in child process to make sure the parent can > check its WCONTINUED. > > CC: Philip Li <philip.li@intel.com> > Reported-by: kernel test robot <lkp@intel.com> > Signed-off-by: Li Zhijian <lizhijian@fujitsu.com> > --- > I have almost forgotten this patch since the former version post over 6 months > ago. This time I just do a rebase and update the comments. > V2: rewrite with pipe to avoid usleep > --- > tools/testing/selftests/pidfd/pidfd_wait.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/tools/testing/selftests/pidfd/pidfd_wait.c b/tools/testing/selftests/pidfd/pidfd_wait.c > index 070c1c876df1..3f7bc6517dea 100644 > --- a/tools/testing/selftests/pidfd/pidfd_wait.c > +++ b/tools/testing/selftests/pidfd/pidfd_wait.c > @@ -95,20 +95,27 @@ TEST(wait_states) > .flags = CLONE_PIDFD | CLONE_PARENT_SETTID, > .exit_signal = SIGCHLD, > }; > + int ret, pfd[2]; > pid_t pid; > siginfo_t info = { > .si_signo = 0, > }; > > + ASSERT_EQ(pipe(pfd), 0); > pid = sys_clone3(&args); > ASSERT_GE(pid, 0); > > if (pid == 0) { > + char buf[2]; > + close(pfd[1]); > kill(getpid(), SIGSTOP); > + ASSERT_EQ(read(pfd[0], buf, 1), 1); > + close(pfd[0]); > kill(getpid(), SIGSTOP); > exit(EXIT_SUCCESS); > } > > + close(pfd[0]); > ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WSTOPPED, NULL), 0); > ASSERT_EQ(info.si_signo, SIGCHLD); > ASSERT_EQ(info.si_code, CLD_STOPPED); > @@ -117,6 +124,8 @@ TEST(wait_states) > ASSERT_EQ(sys_pidfd_send_signal(pidfd, SIGCONT, NULL, 0), 0); > > ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WCONTINUED, NULL), 0); > + ASSERT_EQ(write(pfd[1], "C", 1), 1); > + close(pfd[1]); > ASSERT_EQ(info.si_signo, SIGCHLD); > ASSERT_EQ(info.si_code, CLD_CONTINUED); > ASSERT_EQ(info.si_pid, parent_tid);
On Mon, Jul 18, 2022 at 02:58:39AM +0000, lizhijian@fujitsu.com wrote: > 0Day/LKP observed that the kselftest blocks forever since one of the > pidfd_wait doesn't terminate in 1 of 30 runs. After digging into > the source, we found that it blocks at: > ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WCONTINUED, NULL), 0); > > wait_states has below testing flow: > CHILD PARENT > ---------------+-------------- > 1 STOP itself > 2 WAIT for CHILD STOPPED > 3 SIGNAL CHILD to CONT > 4 CONT > 5 STOP itself > 5' WAIT for CHILD CONT > 6 WAIT for CHILD STOPPED > > The problem is that the kernel cannot ensure the order of 5 and 5', once > 5's goes first, the test will fail. > > we can reproduce it by: > $ while true; do make run_tests -C pidfd; done > > Introduce a blocking read in child process to make sure the parent can > check its WCONTINUED. > > CC: Philip Li <philip.li@intel.com> > Reported-by: kernel test robot <lkp@intel.com> > Signed-off-by: Li Zhijian <lizhijian@fujitsu.com> > --- > I have almost forgotten this patch since the former version post over 6 months > ago. This time I just do a rebase and update the comments. > V2: rewrite with pipe to avoid usleep > --- Thanks for sticking with this! Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
diff --git a/tools/testing/selftests/pidfd/pidfd_wait.c b/tools/testing/selftests/pidfd/pidfd_wait.c index 070c1c876df1..3f7bc6517dea 100644 --- a/tools/testing/selftests/pidfd/pidfd_wait.c +++ b/tools/testing/selftests/pidfd/pidfd_wait.c @@ -95,20 +95,27 @@ TEST(wait_states) .flags = CLONE_PIDFD | CLONE_PARENT_SETTID, .exit_signal = SIGCHLD, }; + int ret, pfd[2]; pid_t pid; siginfo_t info = { .si_signo = 0, }; + ASSERT_EQ(pipe(pfd), 0); pid = sys_clone3(&args); ASSERT_GE(pid, 0); if (pid == 0) { + char buf[2]; + close(pfd[1]); kill(getpid(), SIGSTOP); + ASSERT_EQ(read(pfd[0], buf, 1), 1); + close(pfd[0]); kill(getpid(), SIGSTOP); exit(EXIT_SUCCESS); } + close(pfd[0]); ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WSTOPPED, NULL), 0); ASSERT_EQ(info.si_signo, SIGCHLD); ASSERT_EQ(info.si_code, CLD_STOPPED); @@ -117,6 +124,8 @@ TEST(wait_states) ASSERT_EQ(sys_pidfd_send_signal(pidfd, SIGCONT, NULL, 0), 0); ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WCONTINUED, NULL), 0); + ASSERT_EQ(write(pfd[1], "C", 1), 1); + close(pfd[1]); ASSERT_EQ(info.si_signo, SIGCHLD); ASSERT_EQ(info.si_code, CLD_CONTINUED); ASSERT_EQ(info.si_pid, parent_tid);
0Day/LKP observed that the kselftest blocks forever since one of the pidfd_wait doesn't terminate in 1 of 30 runs. After digging into the source, we found that it blocks at: ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WCONTINUED, NULL), 0); wait_states has below testing flow: CHILD PARENT ---------------+-------------- 1 STOP itself 2 WAIT for CHILD STOPPED 3 SIGNAL CHILD to CONT 4 CONT 5 STOP itself 5' WAIT for CHILD CONT 6 WAIT for CHILD STOPPED The problem is that the kernel cannot ensure the order of 5 and 5', once 5's goes first, the test will fail. we can reproduce it by: $ while true; do make run_tests -C pidfd; done Introduce a blocking read in child process to make sure the parent can check its WCONTINUED. CC: Philip Li <philip.li@intel.com> Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com> --- I have almost forgotten this patch since the former version post over 6 months ago. This time I just do a rebase and update the comments. V2: rewrite with pipe to avoid usleep --- tools/testing/selftests/pidfd/pidfd_wait.c | 9 +++++++++ 1 file changed, 9 insertions(+)